Typical prior art filter systems of the type described above generally include elongate tubular cartridges enclosing a bundle of the microporous hollow fibres. Manifold or header arrangements are then used to connect the cartridges, usually at one or both ends, these manifolds acting to separate and divert the respective flows of contaminated feed and permeate through the system. In this regard, cross-flow systems typically have two feed manifolds (inlet and re-circulation outlet) and one or two permeate manifolds. In cross-flow filtration systems of the prior art the stream to be filtered, flows tangential to or across the surface of the membrane. This generates a sweeping action at the membrane surface, keeping the surface cleaner. Conversely, systems configured for dead end operations have only one feed inlet manifold and one permeate outlet manifold. Further, these prior art manifolds or header arrangements are often configured to facilitate the construction of modular two or three dimensional cartridge arrays.
It should be noted that these systems operate under significant internal pressures. Accordingly, the cartridge casings and header manifold structures need to be made from high strength, and thereby correspondingly high cost, materials such as stainless steel and higher grade reinforced plastic materials specifically designed to withstand these pressures.
Most of the prior art designs available to date have proved satisfactory for small to medium scale applications. However, as there is now an increasing demand for larger scale systems, the current structures are proving to be prohibitively expensive due, for example, to the additional amount of connecting pipe work required and the costs of the componentary associated with each individual cartridge.
When attempting to design larger systems, it is not simply a matter of scaling up all the individual components. This is due, in part, because it is preferred that the individual constituents of the system remain sized so as to be readily man handlable for the purpose of assembly and maintenance. Further, as the structures themselves and associated flow paths get larger, the problems with pressure drops through the system become more significant.
It is an object of the present invention to provide a modified filtration assembly of the kind herein before described which overcomes or substantially ameliorates at least some of the disadvantages of the prior art or at least offers a useful alternative thereto.